The nosh Guide is an extensive handbook for the nosh toolset, complementing the manuals that come with the tools.
It explains the overall ideas of the system, shows how the tools are put together to act in concert in various ways, provides cheatsheets and troubleshooting tips, and provides a small gazetteer of the system.

You can install it from a nosh-guide package on FreeBSD and TrueOS, Debian, and OpenBSD.
It does not require any of the tools themselves to be installed.
You can then open it with the command

The point of the Guide being a self-contained local document is that the time when you most need it will tend to be the time when services, networking, GUI log-on, and other stuff on your system are not working.

You can alternatively read a slightly inferior copy of it at The nosh Guide.
The real Guide has stuff which works in the locally-stored Guide but not so well when viewed served up via some WWW servers.